Three-Port Impedance Model and Validation of VSCs for Stability Analysis

TL;DR

This paper develops and validates a three-port impedance model for VSCs that considers both ac and dc dynamics, enabling comprehensive stability analysis of hybrid AC/DC power systems.

Contribution

It introduces a novel three-port impedance model for VSCs that integrates ac and dc dynamics and provides two stability analysis methods validated through simulations.

Findings

The three-port model accurately predicts stability boundaries.

The GNC-based method effectively assesses system stability.

The pole-zero method offers a quick stability prediction.

Abstract

Modern power system is undergoing a paradigm shift from the synchronous generators-based system to the power electronics converters-dominated system. With the high penetration of converters, serious stability problems are provoked, especially the wideband oscillations. Various studies have been conducted in this respect, while most of them separate the ac-side stability with the dc-side stability. However, for the stability analysis of the hybrid AC/DC grid, it is necessary to consider the converter ac-side and dc-side, simultaneously. In this paper, the stability analysis of voltage source converters (VSCs) considering both ac and dc dynamics is carried out. At first, the three-port AC/DC admittance model of VSCs is established, and the corresponding measurement method from simulations is presented to validate its accuracy. Secondly, based on such three-port model, two stability analysis methods are presented: the one is based on the system open-loop model, where the stability can be judged via the Generalized Nyquist Criterion (GNC); the other one is based on the system closed-loop model, whose stability can be predicted through the pole-zero calculation. At last, a test AC/DC system is built in MATLAB/Simulink, by which the effectiveness of the three-port model-based stability analysis is validated.